Belt tightening and aligning mechanism for abrading devices



M. B. GENTZEL BELT TIGHTENING AND ALIGNING MECHANISM Aug. 2l, 1951 FOR ABRADING DEVICES Filed March 9, 1948 FIG'.

MsLv/N B. GENTZEL INVENTOR.

A TToRNsY Patented Aug. 21, 1951 BELT riGHrENiNG AND ALIGNING MECH- ANIsM Foa AERADING DEVICES Melvin B. Grentzel,v Aurora, Ill., assignor to Independent Pneumatic Tool Company, Chicago, Ill., a corporation of Delaware Application March 9, 1948, Serial No. 13,776

This invention relates to improvements in a belt tightening and aligning mechanism for a portable sanding or abrading device.

The principal object and purpose of my invention is to provider an improved belt tightening and aligning mechanism simple in construction and operation and adaptable to a sanding machine of the portable type without increasing the over all dimensions and/or weight thereof.

A further object and purpose of my invention is to provide such mechanism for the idler drum at the front end of the machine and readily available for adjustment at the front end of the machine.

The invention consists further in the features of construction and combination of parts as hereinafter described and claimed.

In the accompanying drawing- Fig. l is a side View on a reduced scale of a portable power operated sanding or abrading machine embodying my invention;

Fig. 2 is a sectional View taken on line 2 2 of Fig. 1 to show certain details of construction with respect to the belt tightening and aligning mechanism;

Fig. 3 is a longitudinal sectional View taken on line 3 3 of Fig. 2, said sectional view being through the axis element of the idler drum;

Fig. 4 is an end view of the belting tightening and aligning mechanism to more clearly show the knob and adjusting worm wheel and worm to be hereinafter described; and

Fig. 5 is a transverse sectional view taken on line 5 5 of Fig. 2.

In the drawing, I indicates the supporting frame of a portable sanding or abrading machine of the desired size and shape and having a lateral wall 2 at one side to mount a pair of revolvable pulleys or drums 3, 4 at or adjacent `to the opposite ends of the machine as in devices of this character. Trained over the drums 3, l is an endless, flexible, abrading belt 5 approximately as wide as the length of a drum and driven thereby. The outer surface of the belt 5 is provided with a layer 6 of abrading material, such as grains of sand or the like, for smoothing or otherwise treating a work surface against which the belt is applied in the use of the device.

Mounted on the frame I is a gear train l for driving the belt 5 through the rear drum 4 at the desired speed from an electric motor 8 carried by the machine frame I adjacent to its rear handle 9 which may be of the D-type, and is equipped with an electric supply cable or cord v(not shown) for the motor 8. The gear train 3 Claims. (Cl. 51-148) 'I is shown in dotted lines in Fig. 1 and in mesh with the operative teeth on the rear drum 4 and the armature shaft of the motor 8, respectively.

The frame I has a bed or pressure plate I0 to support the lower lap or layer of the belt 5 when pressed against the work surface being operated upon. The machine has a forward handle II adjacent to its front end to be gripped and/or engaged by one hand of the operator in manipulating the machine.

Also, the machine has a dust removing system including a rotary fan I2 at the rear end of the machine and geared into the gear train 1 for operation thereby. The fan I2 has a discharge spout I3 to which a dust collecting bag, also not shown, is connected. The bag is supported from the machine frame I and movable therewith as v a unit. y

The belt tightening and aligning mechanism of my invention is associated with the forward or idler drum 3 and such mechanism is detailed in Figs. 2 to 5, inclusive.

Asthere shown, the drum 3 is mounted on a shaft or axis element I4 journalled in an eccentric or movable means I5 revolvably supported in a tubular bracket or formation I 6 xed to and extending into the drum 3 at its adjacent end, the drum 3 being made hollow and open at its opposite ends for simplicity in construction and lightness in weight. A wear bushing I1 is interposed between the eccentric I5 and the bracket I6 as shown in Figs. 2 and 3.

The inner portion or section I8 of the shaft I4 is within the drum 3 and supports the latter for rotation on ball bearings or the like I9. There is an enlargement 20 on the shaft I4 at its junction with the section I8 to keep the drum 3 in operative position on the shaft portion I8.

Surrounding the bracket IS is a spiral spring 2| having its opposite ends anchored to the frame wall 2 and the eccentric I5 at 22 and 23, respectively, in Fig. 3. The eccentric I5 has a flange 24 at its inner end to which the adjacent end 23 of the spring is secured.

The spring 2| acts normally to turn the eccen tric I5 clockwise as viewed in Fig. 4, to tighten the belt 5. This is accomplished by having the axis means I4 journalled in the member I5 in eccentric relation thereto. Hence turning the eccentric I5 changes the position of the drum 3 laterally towards the forward end of the machine frame I to tighten the belt 5. Turning the eccentric I 5 in the opposite direction or counter-clockwise shifts the position of the axis means I4 laterally to loosen the belt. The extent of Shiftiilg which may be given to the axis means I4 is from the position shown in Fig. 2 to the diametric opposite position. Fig. 3 shows the axis means mid-Way between the limits just mentioned.

The belt is loosened for changing as required for wear or using different grade of abrasive material. Y.The eccentric I5 is turned manually throughits knob 25 fixed tothe eccentric I5 at its outer end slightly beyond the frame wall 2 for grasping by the hand of the operator. Turning the knob 25 against the tensioniof'the spring 2I or counter-clockwise rotates -tieifeccentrici to shift the drum 3 laterally towards the rear drum 4 as shown in Fig. 3. lhis'ireduces'the.'dis tance between the drums lessthan theoperative length of the belt. Releasing the knob 25 allows the spring 2| to swing the ll'drum back, automatically, to tighten the belt 5 and thus increase its tension for drivingfby the tool motor 8.

It will be noted that the shaft or axis section f I8 Which'mounts the "drumffS li'sbent iso lto speak vat an'angleto the shaftlportion I4. -This fdisposes thel center line of .thefd'rum 3 at y'an-"angle fto'the length of the -belt5with the result that -fth'el'same under -a 'disturbing'pressurein the use of the machine or 'otherwise. This angularity '-is-fshownin Fig .32.

1-Ilo change the forementioned angularity A`from time to time as maybe-require'din 'the useof different 'belts, provision is made for 'lturningrthe axisfelement Miby the'operat'or. "This is accom- -fplishedby keying thev shaft I4 l-just vbeyond the Weccentric *I5 'to a Worm lgear i2-6 'which --is r`held `lon fthe shaft by 'bolt `and wa-sher assembly '2"1.

""'Toturnthefvvormgearl-ZG and, =thus theisha't `III, :fa -wormi'28 is lmounted lin the -kriob-25 land has -a turnable element 29 to be engaged betweenthe fingers'oftheoperator.

"Turning the knob 29,I-Whichumayfbe knu'rled,

Vlfprovides fiore-alignment of the idler 'drum f3 fwi-th parts 'ijf th'ebelt tighten'ingaand aligning mecha- ,znism'merein disclosed `maybe changed andrmodi- '.aed withoutfdepartinglfrom :the spirit andscope .iotmytinvention, exceptfas. pointe'dfou-t: in the an- .':nexed claims.

I claim. as my invention:

libran abradi-ng devicefof :the character described, a support, spaced idler and driving drums on said support, an endless abrading belt looped about said drums and driven thereby, a tubular formation xedly secured on and extending through the support, a member revolvably mounted in said tubular formation and projectv-ing beyon'd said Aformation 'exteriorly of' said support, axis'means for said idler 'drurn`journalled in said revolvable member in eccentric relation 'thereto for tightening and loosening the belt on AVturning'the'revolvable member, and means se- Vthebelt, and means for independently'turnirig the memberand the axis element ior'tighteni'ng and-loosening the belt and for varying theangularity of the idler drum,'respectively.

3. In an abrading deviceof the characterdescribed, a support, spaced idler and'driving drums on said support, an endless abradiri'g-belt-f-looped about Isaid drums and driven thereby, a tubular `formation on vthe support,l a 'member 'revolvably mounted in said tubular formation, an axisf'ele- `ment for the idler'drum journalle'din said-inembei' -ineccentric'relation 4thereto and '-for rotation relative thereto and"'h'a'vin'fg v`a Vsectionto `dispose the idler drum 'in angular-relation'to the length ing the member to loosen or tighten the `belt, a Worm gearonth'e'axis element, and a-worm carried 'byfthekn'ob :andmeshingfwith the -worm lggear for-'turning the axis felernent relative to the revolvable member to vary the angularity of the MELVIN 2B. GENTZEL.

AREFERENCES CITED VTheiollowing"references are of record in the 'file of 4this patent:

VUNITED :STATES VP'ATE'Nf'ri-i Number Name A'Date 163:8;965 Tygard Feb. 7, 1899 15686;65-2 Thompson Oct. v9, 1928 v513913574 Vicio -June 13, 1933 '12.282,658 YKneisley May 12, 1942 'l2,'366;527 Heath Jan. 2, v1945 .22,423,737 ITavano. July 8, 1947 

